Bug Fixes:
- support multi-line continuation character (backslash) per CSS2.1 and CSS3 spec (@caiosm1005)
- imported partials should not be compiled (@squarestar)
Enhancements:
- added interface to set/unset variables, i.e., setVariables($array) and unsetVariable($name) (@leafo)
Maintenance:
- micro-optimization replacing is_null() with ! isset() (@Yahasana)